This invention relates to methods for forming epitaxial thin films of perovskite materials via chemical solution deposition. More particularly this invention relates to methods for forming such films through the use of halide precursors. This invention also relates to methods for forming buffer layers to lie between YBCO superconductor layers and metallic or single crystal oxide substrates.
Tremendous interest exists for use of high temperatures superconducting cables for AC power transmission, as roughly half the electric power produced in the U.S. is lost over power lines before reaching the end customer. Production of flexible, kilometer lengths of superconducting wire or tape would enable zero-resistance current transport, recovering this lost power. A major challenge to attaining this goal is achieving a low-cost, high throughput method of producing flexible, epitaxial superconducting films on such length scales. This invention teaches a major advance in production of epitaxial films on flexible, inexpensive base-metal tapes, which enable low-cost, continuous processing of such wires, and other products.
To achieve a needed superconducting power handling capability of about 10.sup.6 A/cm.sup.2, epitaxial or single crystal-like superconducting films of YBa.sub.2 CuO.sub.7-x (YBCO) or similar materials are required. Production of such films likely requires use of a substrate with a similar atomic lattice structure to template crystalline growth. Through cold-rolling of nickel wire, long lengths of (200) oriented nickel tape have been demonstrated by Oak Ridge National Laboratory and others, enabling the required length scales of lattice-matched, oriented, and relatively inexpensive substrates. Superconducting materials such as YBCO would react chemically if deposited directly on nickel. Therefore, some sort of buffer layer is necessary between the YBCO and the nickel substrate.